Core-shell Pigments Research Articles

Fabrication of Al/Ni core–shell pigments via galvanic displacement and their application in radar-infrared compatible stealth coatings

The Al/Ni magnetic core–shell pigments were successfully synthesized in this study using the galvanic displacement method. A dense nickel shell was formed on the surface of a flake Al pigment (Al:Ni2+ = 1:0.5), resulting in a decrease in its lightness by 9 units while only slightly increasing the average infrared emissivity by 0.1 compared with the uncoated flake Al pigments. And it also exhibited soft magnetic characteristics, with a saturated magnetization value of 4.5 emu/g. Moreover, the impact of Al/Ni core-shell pigments on the infrared-radar stealth performance of the target was investigated based on the structure of “low-emissivity coating (LEC) + radar absorbing coating (RAC)”. The results showed that the emissivity of Al/Ni composite coatings maintained a low infrared emissivity (ε ≤ 0.23). The introduction of Ni shell improved the impedance matching between the Al/Ni coating and free space, allowing greater penetration of microwaves into the LEC and improving radar stealth performance of materials. The Al/Ni composite coatings (Al:Ni2+ = 1:0.5, the thickness of RAC:1.2 mm, and LEC: 60 μm) exhibited an extended effective absorption bandwidth (Reflection loss (RL) ≤ −10 dB) from 2.6 to 4.25 GHz and an enhancement of the average RL from −6.43 to −7.1 dB in the range of 2–18 GHz compared to the RAC. Consequently, the Al/Ni magnetic core–shell pigments can be used as novel low-emissivity pigments for infrared-radar compatible stealth research.

Uplifting of anticorrosive coatings performance via TiO2/ZnO core–shell pigment for oil and gas pipelines protection

The objective of this study is to enhance the effectiveness of anticorrosive coatings applied to steel pipelines utilized for the transportation of petroleum products. However, these pipelines are susceptible to corrosion, necessitating the implementation of an economically viable protection system. Therefore, this research endeavors to introduce a novel pigment consisting of titanium dioxide/zinc oxide (TiO2/ZnO) core–shell structure. The pigment is designed to be incorporated into polymeric coating formulations and subsequently subjected to standard testing methods, including immersion tests, adhesion assessments, and electrochemical measurements. The pigment was synthesized and characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), and electron microscopy (SEM and TEM). Electrochemical impedance spectroscopy (EIS) was hired for observing the resistance and capacitance of the formulated coatings through immersion in corrosive medium (3.5% NaCl). The obtained results conveyed that the prepared core–shell pigment with its unique structure had strongly elevated the resistivity of the formulated coating, which enhanced its role in the protection of the pipeline wall from corrosion.

Sustainable coatings based on core–shell pigments to enhance antibacterial and other beneficial paper properties

Paper manufacturers are constantly looking for new methods to improve coated paper properties. Pigments are encountered in paper coatings to add new functions. For example, titanium dioxide (TiO2 ) and talc are considered among the best-known pigments used in paper coating and manufacturing due to their whiteness and other beneficial properties. Nevertheless, talc has a weak dispersion during which its particles agglomerate, and this disadvantage needs to be overcome before its application which means higher cost. Therefore, in this work, a core–shell technique is used to modify the talc surface and enhance its dispersion in order to promote its use in improving the properties of the paper. Core–shell pigments are composed of a thin shell of (nano- and micronized) titanium dioxide precipitated on talc particles. These prepared talc/TiO2 core–shell pigments were characterized using various techniques such as XRF, SEM, and TEM, and then they were incorporated in paper coatings to evaluate their effect on the different properties of the coated papers. The results showed that nano-talc/TiO2 with the obtained unique chemical and morphological structure has improved the physical, mechanical, and optical properties of the coated papers besides improving their antimicrobial activity, especially when compared to papers coated with micronized talc/TiO2.

Exploration on ability of printable modified papers for the application in heat sublimation transfer printing of polyester fabric

In this work heat transfer papers were loaded with a new core–shell pigment based on precipitating thin shell of titanium dioxide on a core of rice husk silica ash TiO2/RHSA to be applied in dye sublimation printing of textile fabrics. Besides, 0.1% (w/w) cationic polyacrylamide (CPAM) and 1% (w/w) bentonite (Bt) were also added sequentially to improve drainage and filler retention of the paper hand-sheets made from bleached kraft bagasse pulps. The effect of the new core–shell pigment on the mechanical and barrier properties, thermal stability and surface morphology of modified paper sheets were investigated. In addition, the study of transfer printability and ease of dye release from paper to fabric in this heat transfer printing of polyester fabrics using silk-screen printing under different transfer parameters were studied. Also, fastness measurements including washing, light and perspiration of printing polyester fabric were also estimated.

Generation of novel, hygienic, inhibitive, and cost-effective nanostructured Core-shell pigments

The key goal of this study is to develop new, eco-friendly, and cost-effective nanostructured core-shell pigments based on nanosilica extracted from rice husk agro-waste to offer both anticorrosive and antimicrobial characteristics. The nanostructured core-shell pigments were created by depositing a thin shell of ZnO and/or CuO nanoparticles over a low-cost core of nanosilica extracted from rice husk agricultural waste. The synthesized pigments were characterized using X-ray diffraction, X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray, and transmission electron microscopy. These pigments were incorporated into alkyd resin to evaluate their antimicrobial and anticorrosive performance. Immersion tests, electrochemical impedance spectroscopy, and scanning electron microscopy were used to determine the corrosion resistance of coatings containing the prepared nanostructured core-shell pigments. The results deduced that the coating resistance followed the sequence ZnO.CuO/Si > ZnO/Si > CuO/Si > nanosilica. Furthermore, the antimicrobial activity of these coatings was investigated using disk diffusion and shake flask methods. The results revealed that coatings containing the prepared pigments could offer good antimicrobial activity. This research shows that these novel nanostructured core-shell pigments may act as anticorrosive and antimicrobial pigments in a single-layered coating at a low cost. Additionally, because they are constructed mainly of nano-silica recovered from agro-waste and have a low concentration of heavy metals, these pigments are both cost-effective and eco-friendly.

New out-performing structured pigments for anticorrosive practical applications

PurposeLong time ago, multistructured materials showed great interest being considered as the bridge between bulk and atomic materials. Core-shell particles are kind of composite materials that refer to multilayered structures with a core totally surrounded by shell(s) (onion-like structure). These new structures can offer an advantage of applying new adjustable parameters like shape, stoichiometry and chemical ordering, in addition to the opportunity of tailoring more complexed structures for different applications. Recently it was found that these structures can be tuned and taken for more advanced path with novel structures formed of core surrounded by multishells. The purpose of this study is to study the effect of the new anticorrosive pigments with its mutual shells and how each shell affects the performance of the pigment in protecting the metal and which shell will be more relevant in its effect.Design/methodology/approachThe prepared pigments were characterized using X-ray fluorescence, X-ray diffraction, TEM and SEM/EDX to prove their core-shell structure, and then they were integrated in coating formulations to evaluate their anticorrosive activity using immersion test and electrochemical impedance spectroscopy (EIS).FindingsThe results showed that the prepared core-shell pigments possess a lot of unique characteristics and can offer improved anticorrosive performance in the generated coatings.Originality/valueCore-mutual shells structured pigments were prepared for improving the corrosion resistivity of the organic coatings as a new trend in anticorrosive pigments.

A State-of-the-Art Review on Core–Shell Pigments Nanostructure Preparation and Test Methods

Uses of novel technologies for improving the durability and lifespan of the construction materials have emerged as viable solutions toward the sustainable future wherein the coating industry plays a significant role in economy growth and better livelihoods. Thus, the continual innovation of various technologies to introduce diverse market products has become indispensable. Properties of materials like color stability under UV, elevated temperatures and aggressive environments, and skid and abrasion resistance are the main challenges faced by commercial coating materials, leading to more demand of natural materials as sustainable agents. Lately, nanostructured core–shell pigments with unique compositions have widely been utilized in composite materials to enhance their properties. Core–shell particles exhibit smart properties and have immense benefits when combined with building materials. Based on these facts, we comprehensively overviewed the state-of-the-art research of core–shell nanomaterials in terms of their preparation and performance evaluation methods, as well as feasible applications. The first part of this article discusses effective shell materials, including most common silica and titanium oxides. In addition, nanotechnology enabling the production and patterning of low-dimensional materials for widespread applications is emphasized. The second part deals with various potential core materials used to achieve core–shell nanostructures. The third part of this paper highlights some interesting mechanisms of core–shell structures in the modified systems that display high stability, durability, efficiency, and eco-friendliness. Finally, different applications of these core–shell nanostructures are underscored together with their test methods to evaluate their performances.

Protective primers with reduced zinc powder content caused by the addition of core-shell micro talc/polyaniline pigment

This study aims to verify the possibility of replacing a portion of zinc (up to 30 wt.%) with a newly designed micro talc/polyaniline (PANI) core-shell pigment that can be used in the protective primer compositions for metals. Measurements of the electrode potential of painted steel and the electrical capacity of the steel/coating/electrolyte system showed that synthesized pigment bears two functions. Firstly, its presence in the epoxy-amine coatings provides a cathodic protection mechanism for steel with the lower zinc content. Secondly, it allows long-term preservation of the sacrificial metal activity and passive state of the substrate due to the autocatalytic redox cycle based on the reversible conversion of PANI from its emeraldine to leucoemeraldine form. The corresponding mechanism that allows the retaining of sacrificial metal activity and the passive state of the substrate is proposed.

Inorganic Mn-Based Core–Shell Pigments by Solution-Combustion Synthesis with Citric Acid as a Fuel

Inorganic Mn-Based Core–Shell Pigments by Solution-Combustion Synthesis with Citric Acid as a Fuel

Influence of Anticorrosive Coatings Integrated with Novel Core–Shell Pigment on the Corrosion Protection of Pipelines in CO2 Environment

Interior corrosion of pipelines is a major and costly problem encountered in the oil and gas industry. Regarding this problem, coating systems based on waterborne and solvent-based binders integrated with novel core–shell pigment are formulated to maintain excellent mechanical and corrosion resistance. The novel pigment was synthesized using core–shell technique by precipitating layer of zinc and cobalt oxides on the surface of aluminum foil waste. Mechanical testing and electrochemical studies of coatings demonstrated that the integration of polyurethane and acrylic emulsion with the core–shell pigment can enhance the mechanical and corrosion resistivity. The results obtained in this work can be onset to the future use of treated wastes to enhance coating systems for corrosion protection purposes.

A novel rutile TiO2/AlPO4 core-shell pigment with substantially suppressed photoactivity and enhanced dispersion stability

Decorating inorganic particles with core-shell structure is an attractive approach to broaden their practical application owing to the synergistic effects between inner core and outer shell. In this work, a novel rutile TiO2@AlPO4 core-shell composite has been constructed via a facile one-step wet chemical deposition method. The dense and thick AlPO4 shell can hinder direct contact between TiO2 core and outer environment, decrease light absorption ability, suppress separation of electron-hole pairs, and accelerate electron annihilation. Such unique properties hindered the generation of reactive oxygen species, further contributing to the suppression of photoactivity. The superior dispersion stability in aqueous system of TiO2@AlPO4 core-shell hybrid was attributed to its enhanced surface electronegativity. Thus-produced TiO2@AlPO4 core-shell hybrid with suppressed photoactivity and enhanced dispersion stability could further increase the weather durability and prolong the life span of TiO2-based pigment. Overall, this study provides new insight into the mass production of multi-functional rutile TiO2 pigments.

Evaluation of new core-shell pigments on the anticorrosive performance of coated reinforced concrete steel

Pigments are considered as the major content of paints that can help in preventing corrosion. In this work, epoxy based pait system was applied on reinforced concrete steel to evaluate its anticorrosive performance. This system is based on new core-shell pigments which are composed of a core of different calcium carbonate sources (natural calcite, marble waste and eggshell) covered with thin shell of zinc ferrite to compare their anticorrosive effect. The corrosion resistance of the coatings was evaluated in 3.5 % NaCl for 28 days via two electrochemical methods; open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The measurements revealed that coated concrete steel with paints containing zinc ferrite/marble was the best in its corrosion protection performance showing that although the cores are all based on calcium carbonate, the source can affect the performance.

Polymer Coatings Containing Core-Shell Pigments with Polyaniline Shell

The effect exerted on rheological properties of polymer compounds by core-shell pigments with a shell of doped and undoped polyaniline was studied. In the presence of core-shell pigments with a doped polyaniline shell, the limiting content of the gel fraction increases, but the polymer network becomes less dense. Polarization studies show that the use of pigments with an undoped polyaniline shell leads to stronger inhibition of the corrosion process. As shown by electrochemical impedance spectroscopy, introduction of core—shell pigments enhances the protective properties of the coatings formed.

Enhanced ink-absorption performance of inkjet printing paper-based patterns with core-shell-structure CaCO3{\mathrm{CaCO}_{3}}@SiO2{\mathrm{SiO}_{2}} pigments

Abstract The inorganic core-shell pigment CaCO 3 {\mathrm{CaCO}_{3}} @ SiO 2 {\mathrm{SiO}_{2}} was synthesized using a sol-gel method, and the pigment was applied as a surface coating on inkjet paper to study the influence of inorganic core-shell pigments on the dynamic permeability, surface properties, optical properties and inkjet-printing performance of coated paper. CaCO 3 {\mathrm{CaCO}_{3}} @ SiO 2 {\mathrm{SiO}_{2}} prepared using carboxymethyl cellulose (CMC) had better coverage than that prepared using polystyrene sodium sulfate (PSS) dispersant. The CMC-prepared CaCO 3 {\mathrm{CaCO}_{3}} @ SiO 2 {\mathrm{SiO}_{2}} -a had improved dispersibility, and the solids content of the coating reached 35 %. Inorganic core-shell pigments improve the surface and optical properties of the coated paper, making them similar to those of a reference calcium carbonate-coated paper. The smoothness and gloss improved by 60.8 % and 78.4 %, respectively, compared with those of silica-coated paper. The inkjet solid density and dot definition increased by 28.8 % and 4.1 %, respectively, compared with those of the calcium carbonate-coated paper. Preparing inorganic core-shell pigment CaCO 3 {\mathrm{CaCO}_{3}} @ SiO 2 {\mathrm{SiO}_{2}} is an effective method to fabricate inkjet printing coatings with advantageous microstructures for ink absorption.

Performance of coatings containing treated silica fume in the corrosion protection of reinforced concrete

PurposeThis study aims to apply novel anticorrosive pigments containing silica fume-phosphates (Si-Ph), which were prepared using core-shell technique by covering 80-90 per cent silica fume (core) with 10-20 per cent phosphates (shell) previously, to play dual functions simultaneously as anticorrosive pigments in coating formulations and as an anticorrosive admixture in concrete even if it is not present in the concrete itself. Two comparisons were held out to show the results of coatings on rebars containing core-shell pigments in concrete, and concrete admixtured with silica fume can perform a dual function as anticorrosive pigment and concrete admixture. The evaluation of corrosion protection efficiency of coatings containing core-shell pigments and those containing phosphates was performed.Design/methodology/approachSimple chemical techniques were used to prepare core-shell pigments, and their characterization was carried out in a previous work. These pigments were incorporated in solvent-based paint formulations based on epoxy resin. Different electrochemical techniques such as open-circuit potential and electrochemical impedance spectroscopy were used to evaluate the anticorrosive efficiency of the new pigments.FindingsThe electrochemical measurements showed that concrete containing coated rebars with core-shell pigments exhibited almost similar results to that of concrete admixtured with silica fume. Also, the anticorrosive performance of coatings containing Si-Ph pigments offered protection efficiency almost similar to that of phosphates, proving that these new pigments can perform both roles as anticorrosive pigment and concrete admixture.Originality/valueAlthough the new Si-Ph pigments contain more than 80 per cent waste material, its performance can be compared to original phosphate pigments in the reinforced concrete.

The Effect of Processing Parameters on the Formation and Properties of Al/Ni Core-Shell Pigments via a Galvanic Displacement Method

Al/Ni bimetallic core-shell pigments with flake Al particle as core and metallic Ni as shell were synthesized via a galvanic displacement method and studied with X-ray diffraction, scanning electron micrograph (SEM), specific surface area analysis (BET), thermogravimetry-differential thermalanalysis (TG/DSC), and visible-near infrared-infrared reflectance spectroscopy. The influence of reactant ratio (Al:Ni2+) and order of addition on phase structure, surface morphology, optical properties, and high temperature oxidation resistance properties were studied systematically. The results show that the local concentration of Ni2+ at solid-liquid interfaces can be effectively modulated by adjusting the reactant ratio and order of addition. A high local concentration of Ni2+ improves the rate of displacement reaction resulting in more metallic Ni on the surface of the flake Al powders. This increases the relative content of Ni in the shell. The change of displacement reaction rate also leads to a different surface morphology and roughness of the Ni shell. The thick and rough Ni shell has a strong absorption extinction due to the intense light scattering and absorption-this substantially reduces the spectral reflectance of the flake Al core. Infrared reflectance in particular is influenced by light scattering and absorption of the rough surface. In addition, the Ni shell can enhance the high temperature oxidation resistance of the Al core by preventing contact between the metallic Al substrate and oxygen. The oxidation resistance is also associated with the processing parameters of the galvanic displacement reaction.

Preparation of γ-Ce2S3@ZrO2 Red Pigment by Hydrolysis Combined Hydrothermal Two Steps Method

The core-shell red pigment γ-Ce2S3@ZrO2 was prepared by a two step method. γ-Ce2S3 was pre-coated at 30°C with hydrolysis, followed by hydrothermal reaction at 180 °C for further coating and crystallization. The effect of preparation method, hydrolysis dropping speed and the number of hydrothermal process on the microstructure of the ZrO2 layer was observed. The influence of coating layer to chromaticity, heat resistance and acid stability was also investigated. The results show that a complete layer at nearly 90 nm coated on the surface of the γ-Ce2S3 particles. The as-prepared pigment exhibited pure red color (L* = 44.38, a* = 31.94, b* = 23.14). Moreover, this coating layer can provide protection to pigment particles. The core-shell pigment can remain red color (L* = 42.71, a* = 26.23, b* =18.38) after calcined in air at 380 °C, while uncoated pigment turned to grey dark at 360 oC.

Corrosion protection performance of silica fume waste-phosphates core-shell pigments

PurposeNew types of phosphate pigments which are appropriate alternatives for hazardous chromate pigments have been prepared and evaluated. These new pigments were prepared via a new technique named core-shell. The core-shell materials consist of at least two separate phases with different chemical compositions. Recently, these materials have become more significant because they have the advantage of gathering the properties of both cores and shells that help to overcome the defects that they might possess individually. The purpose of this research is to develop a modified silica fume-phosphate core-shell pigment that contains 80-90 per cent of waste material (silica fume) and at the same time can offer promoted mechanical and anticorrosive properties than silica fume and they can also be compared with phosphates. The pigments have shells of Zn, Mn, Zn.Mn phosphates comprising about 10-20 per cent.Design/methodology/approachThe prepared core-shell pigments have been characterized using several methods, which have then been integrated in alkyd paint formulations. The physical and mechanical properties of dry films and their corrosion prevention using accelerated laboratory test in 3.5 per cent NaCl for 28 days are estimated.FindingsThis study showed that the performance of these new pigments is highly efficient in corrosion protection, and it can be a suitable alternative to phosphate pigments despite containing phosphates which does not exceed 20 per cent of the composition.Practical implicationsWaste materials were reused in paints and only simple modification was used; their effectiveness was high and can be compared with well-known pigments.Originality/valueSilica-phosphate core-shell pigments are environmentally friendly pigments that can replace other hazardous pigments (e.g. chromates and phosphates) with almost the same quality in their performance.

Evaluation of the anticorrosive performance of epoxy coatings containing new core/shell pigments

Purpose Core-shell is structured particles having several chemical compositions. The advantage of these particles arise from their specific design, to be used in decreasing costs by using inexpensive material (natural ore or waste material) as carrier for thin shell of active material. This study aims to prepare ferrites/silica core-shell pigments and compare their inhibition efficiency to original ferrites. These pigments have shells of different ferrites that comprise 10-15 per cent of the prepared pigments on silica fume. Silica fume which is the core is a byproduct in the ferro–silicon industry; this core comprises 85-90 per cent of the prepared pigments. Design/methodology/approach The prepared core-shell pigments were characterized using transmission electron microscopy analysis, energy-dispersive X-ray analysis and sequential wavelength dispersive X-ray fluorescence. These pigments were integrated in epoxy-based paint formulations, and the physical, mechanical and corrosion properties of dry films were examined. The corrosion properties were studied by using immersion test in 3.5 per cent NaCl for 28 days. Findings This study showed that these new eco-friendly and inexpensive pigments are similar to ferrites in their inhibition performance, i.e. they exhibited high corrosion prevention. Research limitations/implications Domestic waste materials were reused in paints and only simple modification was used, and then, their effectiveness showed similar performance to that of the original pigments. Originality/value Ferrite and ferrite/silica pigments are environmentally friendly pigments that can replace other hazardous pigments (e.g. chromates) with almost the same quality in their performance; also, they can be used in industries other than paints (e.g. paper, rubber and plastics composites).

Anticorrosive efficiency of alkyd resin-based coatings containing Mg–Zn–Fe mixed oxide-based pigments

Abstract Mixed oxide-based pigments Mg–Zn–Fe with different particle morphologies were prepared by high-temperature solid phase reactions. The core shell pigments containing ferric oxide and non-isometric particles of layered silicates were also prepared. The pigments were tested in paints, the pigment volume concentrations in the modified alkyd resin based binder being 5%, 10%, and 15%. The paint properties were examined by accelerated corrosion tests and by physico-mechanical tests. The effect of the pigment particle morphology on the surface hardness of the paint films was also studied. The influence of pigment volume concentration on the coating properties, and the optimum concentrations providing the most efficient anticorrosive protection were processed. A higher anticorrosion efficiency was observed for the paints with pigments possessing the lamellar particle shape.